1. Field of the Invention
The present invention relates to battery control devices which perform estimation of a chargeable/dischargeable electric power of a rechargeable battery.
2. Description of the Related Art
For example, when a rechargeable battery mounted on a motor vehicle, i.e. an in-vehicle battery is charged with regenerative power generated by a regenerative power generation process, a battery control device mounted to a motor vehicle estimates a magnitude of a chargeable electric power with which the rechargeable battery is fully charged. In addition, the battery control device estimates a magnitude of a dischargeable electric power to be discharged from the rechargeable battery during a period of supplying an electric power from the rechargeable battery to a main motor mounted on the motor vehicle.
There is a conventional technique, for example a Japanese patent laid open publication No. 2010-203935, discloses an estimation device capable of estimating a magnitude of a chargeable/dischargeable electric power of a rechargeable battery mounted on a motor vehicle. This conventional estimation device estimates a chargeable electric power and a dischargeable electric power of the rechargeable battery on the basis of the assumption that a change amount of a terminal voltage of the rechargeable battery is substantially equal to a change amount of a voltage caused by a current change of a current flowing in the rechargeable battery.
The electric power charging and discharging operation is repeatedly performed in the rechargeable battery mounted on the motor vehicle at predetermined time intervals. During the charging and discharging operation in the predetermined period of time, electric charge is accumulated in the rechargeable battery. That is, when such electric charge is inputted to/outputted from the rechargeable battery through the terminals of the rechargeable battery during the electric power charging/discharging period, a part of the electric charge is accumulated in the rechargeable battery.
During the accumulation of electric charge in the rechargeable battery, a change amount of the terminal voltage of the rechargeable battery contains a first voltage change component and a second voltage change component. That is, the first voltage change component is obtained by a multiplication between an internal resistance value of the rechargeable battery and a current flowing in the rechargeable battery. The second voltage change component is obtained by the accumulation of electric charge in the rechargeable battery. In this case, the conventional technique, for example, Japanese patent laid open publication No. 2010-203935 does not consider the second voltage change component. That is, the conventional technique does not consider the second voltage change component caused by the change amount of electric charge (accumulation of electric charge in or discharging of electric charge from the rechargeable battery. The conventional technique previously described deteriorates an estimation accuracy of the terminal voltage of the rechargeable battery. As a result, the conventional technique has a drawback of it being difficult to estimate a correct amount of a chargeable electric power with which the rechargeable battery is fully charged and a dischargeable electric power of the rechargeable battery mounted on a motor vehicle with high accuracy.